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Abstract:

A compensation film includes a first retardation layer including a
polymer having negative birefringence, and a second retardation layer
including a liquid crystal having positive birefringence, where the first
retardation layer has an in-plane retardation (Re1) of 320 nm to
1050 nm for incident light having wavelength of 550 nm, the second
retardation layer has an in-plane retardation (Re2) of 180 nm to 910
nm for the incident light, an entire in-plane retardation (Re0) of
the first and second retardation layers for the incident light is a
difference between the in-plane retardations of the first and second
retardation layers, an angle between slow axes of the first and second
retardation layers is 85 to 95 degrees, and the entire in-plane
retardation (Re0) of the first and second retardation layers for the
wavelength of 450 nm, 550 nm and 650 nm satisfies Re0 (450
nm)<Re0 (550 nm)<Re0 (650 nm).

Claims:

1. A compensation film comprising: a first retardation layer comprising a
polymer having negative birefringence; and a second retardation layer
comprising a liquid crystal having positive birefringence, wherein the
first retardation layer has an in-plane retardation (Re1) in a range
of about 320 nm to about 1050 nm for incident light having a wavelength
of about 550 nm, the second retardation layer has an in-plane retardation
(Re2) in a range of about 180 nm to about 910 nm for the incident
light having the wavelength of about 550 nm, an entire in-plane
retardation (Re0) of the first retardation layer and the second
retardation layer for the incident light having the wavelength of about
550 nm is a difference between the in-plane retardation (Re1) of the
first retardation layer and the in-plane retardation (Re2) of the
second retardation layer, an angle between a slow axis of the first
retardation layer and a slow axis of the second retardation layer is in a
range of about 85 degrees to about 95 degrees, and the entire in-plane
retardation (Re0) of the first retardation layer and the second
retardation layer for the wavelength of about 450 nm, about 550 nm and
about 650 nm satisfies the following inequation: Re0 (450
nm)<Re0 (550 nm)<Re0 (650 nm).

2. The compensation film of claim 1, wherein the entire in-plane
retardation (Re0) of the first retardation layer and the second
retardation layer for the incident light having the wavelength of about
550 nm is in a range of about 120 nm to about 160 nm.

3. The compensation film of claim 1, wherein the first retardation layer
has a short wavelength dispersion in a range of about 1.00 to about 1.15,
and the second retardation layer has a short wavelength dispersion in a
range of about 1.05 to about 1.30.

4. The compensation film of claim 1, wherein the first retardation layer
has a long wavelength dispersion in a range of about 0.90 to about 1.00,
and the second retardation layer has a long wavelength dispersion in a
range of about 0.80 to about 0.99.

5. The compensation film of claim 1, wherein the compensation film has a
short wavelength dispersion greater than or equal to about 0.7 and less
than about 1.0, and the compensation film has a long wavelength
dispersion greater than about 1.0 and less than or equal to about 1.2.

6. The compensation film of claim 1, wherein a thickness direction
retardation (Rth1) and the in-plane retardation (Re1) of the
first retardation layer for the incident light having the wavelength of
about 550 nm satisfy the following Inequation:
-2.0.ltoreq.(Rth1/Re1)+0.5.ltoreq.0.5, and a thickness
direction retardation (Rth2) and the in-plane retardation (Re2)
of the second retardation layer for the incident light having the
wavelength of about 550 nm satisfy the following Inequation:
1.0.ltoreq.(Rth2/Re2)+0.5.ltoreq.1.5.

7. The compensation film of claim 1, wherein a thickness direction
retardation (Rth0) and the in-plane retardation (Re0) of the
compensation film for the incident light having the wavelength of about
550 nm satisfy the following inequation:
-1.0.ltoreq.(Rth0/Re0)+0.5.ltoreq.1.0.

8. The compensation film of claim 1, wherein the first retardation layer
is an elongated polymer layer, and the first retardation layer has a
refractive index simultaneously satisfying the following inequations:
nx1.gtoreq.ny1, and nx1.gtoreq.nz1, wherein nx1
denotes a refractive index at a slow axis of the first retardation layer,
ny1 denotes a refractive index at a fast axis of the first
retardation layer, nz1 denotes a refractive index in a direction
perpendicular to the slow and fast axes of the first retardation layer.

9. The compensation film of claim 1, wherein the second retardation layer
is an anisotropic liquid crystal layer, and the second retardation layer
has a refractive index simultaneously satisfying the following
inequations: nx2.gtoreq.ny2, and nx2.gtoreq.nz2,
wherein nx2 denotes a refractive index at a slow axis of the second
retardation layer, ny2 denotes a refractive index at a fast axis of
the second retardation layer, and nz2 denotes a refractive index in
a direction perpendicular to the slow and fast axes of the second
retardation layer.

10. The compensation film of claim 1, wherein the compensation film has a
refractive index satisfying the following inequation:
nx0>nz0>ny0, wherein nx0 denotes a refractive
index at a slow axis of the compensation film, ny0 denotes a
refractive index at a fast axis of the compensation film, and nz0
denotes a refractive index in a direction perpendicular to the slow and
fast axes of the compensation film.

12. The compensation film of claim 1, wherein the liquid crystal is a
reactive mesogen liquid crystal.

13. The compensation film of claim 12, wherein the reactive mesogen
liquid crystal comprises a rod-shaped aromatic derivative having a
reactive cross-sectional group, propylene glycol 1-methyl, propylene
glycol 2-acetate, a compound represented by P1-A1-(Z1-A2)n-P2, or a
combination thereof, wherein P1 and P2 each independently comprises
acrylate, methacrylate, vinyl, vinyloxy, epoxy, or a combination thereof,
A1 and A2 each independently comprises 1,4-phenylene,
naphthalene-2,6-diyl group, or a combination thereof, Z1 comprises a
single bond, --COO--, --OCO--, or a combination thereof, and n is 0, 1 or
2.

14. An optical film comprising: a polarizer element; and the compensation
film of claim 1.

15. A display device comprising: a display panel; a compensation film
disposed on the display panel; and a polarizer element disposed on the
compensation film, wherein the compensation film comprises: a first
retardation layer comprising a polymer having negative birefringence; and
a second retardation layer comprising liquid crystal having positive
birefringence, wherein the first retardation layer has an in-plane
retardation (Re1) in a range of about 320 nm to about 1050 nm for
incident light having a wavelength of about 550 nm, the second
retardation layer has an in-plane retardation (Re2) in a range of
about 180 nm to about 910 nm for the incident light having the wavelength
of about 550 nm, an entire in-plane retardation (Re0) of the first
retardation layer and the second retardation layer for the incident light
having the wavelength of about 550 nm is a difference between the
in-plane retardation (Re1) of the first retardation layer and the
in-plane retardation (Re2) of the second retardation layer, the
entire in-plane retardation (Re0) of the first retardation layer and
the second retardation layer for the wavelength of about 450 nm, about
550 nm, and about 650 nm satisfies Re0 (450 nm)<Re0 (550
nm)<Re0 (650 nm), and an angle between a slow axis of the first
retardation layer and a slow axis of the second retardation layer is in a
range of about 85 degrees to about 95 degrees.

16. The display device of claim 15, wherein the first retardation layer
has a short wavelength dispersion in a range of about 1.00 to about 1.15,
the second retardation layer has a short wavelength dispersion in a range
of about 1.05 to about 1.30, the first retardation layer has a long
wavelength dispersion in a range of about 0.90 to about 1.00, the second
retardation layer has a long wavelength dispersion in a range of about
0.80 to about 0.99, an entire short wavelength dispersion of the first
retardation layer and the second retardation layer is greater than or
equal to about 0.7 and less than about 1.0, and an entire long wavelength
dispersion of the first retardation layer and the second retardation
layer is greater than about 1.0 and less than or equal to about 1.2.

17. The display device of claim 15, wherein a thickness direction
retardation (Rth1) and the in-plane retardation (Re1) of the
first retardation layer for the incident light having the wavelength of
about 550 nm satisfy the following Inequation:
-2.0.ltoreq.(Rth1/Re1)+0.5.ltoreq.0.5, a thickness direction
retardation (Rth2) and the in-plane retardation (Re2) of the
second retardation layer for the incident light having the wavelength of
about 550 nm satisfy the following inequation:
1.0.ltoreq.(Rth2/Re2)+0.5.ltoreq.1.5, and an entire thickness
direction retardation (Rth0) and the entire in-plane retardation
(Re0) of the first retardation layer and the second retardation
layer for the incident light having the wavelength of about 550 nm
satisfy the following Inequation:
-1.0.ltoreq.(Rth0/Re0)+0.5.ltoreq.1.0.

Description:

[0001] This application claims priority to Korean Patent Application No.
10-2013-0137146 filed on Nov. 12, 2013, and all the benefits accruing
therefrom under 35 U.S.C. §119, the contents of which are
incorporated by reference herein in its entirety.

BACKGROUND

[0002] 1. Field

[0003] Embodiments of the invention relate to a compensation film, an
optical film, and a display device including the compensation film or the
optical film.

[0004] 2. Description of the Related Art

[0005] A flat panel displays may be classified into a light-emitting
display device that emits light by itself and a non-emissive display
device that includes a separate light source, and a compensation film
such as a retardation film is generally employed for improving the image
quality thereof.

[0006] In the case of the light emitting display device, for example, an
organic light emitting diode ("OLED") display, the visibility and the
contrast ratio may be deteriorated by reflection of the exterior light
caused by a metal such as an electrode. To reduce the deterioration in
the visibility and the contrast ratio, the linear polarized light is
shifted into circularly polarized light by using a polarizer and a
compensation film, so that reflection of the external light by the OLED
display and leakage thereof to the outside may be effectively prevented.

[0007] To reduce the reflection of the exterior light, a liquid crystal
display ("LCD"), which is a non-emissive display device, changes the
linear polarized light into the circularly polarized light to improve the
image quality according to the type of the device such a transparent
type, a transflective type, or a reflective type, for example.

[0008] However, a conventional compensation film is strongly dependent
upon the wavelength to the incident light, so such a compensation film
may effectively operate for light having a certain wavelength, but the
effect thereof may be deteriorated for other wavelengths. In addition, a
conventional compensation film may have strong viewing angle dependency.

SUMMARY

[0009] One embodiment provides a compensation film with improved display
characteristics by reducing the wavelength dependency and the viewing
angle dependency.

[0010] Another embodiment provides an optical film including the
compensation film.

[0011] A further embodiment provides a display device including the
compensation film.

[0012] According to an embodiment, a compensation film includes a first
retardation layer including a polymer having negative birefringence, and
a second retardation layer including a liquid crystal having positive
birefringence, where the first retardation layer has an in-plane
retardation (Re1) in a range of about 320 nanometers (nm) to about
1050 nm for incident light having a wavelength of about 550 nm, the
second retardation layer has an in-plane retardation (Re2) in a
range of about 180 nm to about 910 nm for the incident light having the
wavelength of about 550 nm, the entire in-plane retardation (Re0) of
the first retardation layer and the second retardation layer for the
incident light having the wavelength of about 550 nm is determined by a
difference between the in-plane retardation (Re1) of the first
retardation layer and the in-plane retardation (Re2) of the second
retardation layer, an angle between a slow axis of the first retardation
layer and a slow axis of the second retardation layer is about 85 to
about 95 degrees, and the entire in-plane retardation (Re0) of the
first retardation layer and the second retardation layer for wavelengths
of about 450 nm, 550 nm, and 650 nm satisfy Re0 (450 nm)<Re0
(550 nm)<Re0 (650 nm).

[0013] In an embodiment, the entire in-plane retardation (Re0) of the
first retardation layer and the second retardation layer for the incident
light having the wavelength of about 550 nm may be in a range of about
120 nm to about 160 nm.

[0014] In an embodiment, the first retardation layer may have a short
wavelength dispersion in a range of about 1.00 to about 1.15, and the
second retardation layer may have a short wavelength dispersion in a
range of about 1.05 to about 1.30.

[0015] In an embodiment, the first retardation layer may have a long
wavelength dispersion in a range of about 0.90 to about 1.00, and the
second retardation layer may have a long wavelength dispersion in a range
of about 0.80 to about 0.99.

[0016] In an embodiment, the compensation film may have a short wavelength
dispersion greater than or equal to about 0.7 and less than about 1.0,
and the compensation film may have a long wavelength dispersion greater
than about 1.0 and less than or equal to about 1.2.

[0017] In an embodiment, a thickness direction retardation (Rth1) and
the in-plane retardation (Re1) of the first retardation layer for
the incident light having the wavelength of about 550 nm may satisfy the
following inequation: -2.0≦(Rth1/Re1)+0.5≦0.5,
and a thickness direction retardation (Rth2) and the in-plane
retardation (Re2) of the second retardation layer for the incident
light having the wavelength of about 550 nm may satisfy the following
inequation: 1.0≦(Rth2/Re2)+0.5≦1.5.

[0018] In an embodiment, a thickness direction retardation (Rth0) and
the in-plane retardation (Re0) of the compensation film for the
incident light having the wavelength of about 550 nm may satisfy the
following inequation: -1.0≦(Rth0/Re0)+0.5≦1.0.

[0019] In an embodiment, the first retardation layer may be an elongated
polymer layer, and the first retardation layer may have a refractive
index simultaneously satisfying the following inequations:
nx1≧ny1; and nx1≧nz1, where nx1
denotes a refractive index at a slow axis of the first retardation layer,
ny1 denotes a refractive index at a fast axis of the first
retardation layer, and nz1 denotes a refractive index in a direction
perpendicular to the slow and fast axes of the first retardation layer.

[0020] In an embodiment, the second retardation layer may be an
anisotropic liquid crystal layer, and the second retardation layer may
have a refractive index simultaneously satisfying the following
inequations: nx2≧ny2, and nx2≧nz2,
where nx2 denotes a refractive index at a slow axis of the second
retardation layer, ny2 denotes a refractive index at a fast axis of
the second retardation layer, and nz2 denotes a refractive index in
a direction perpendicular to the slow and fast axes of the second
retardation layer.

[0021] In an embodiment, the compensation film may have a refractive index
satisfying the following inequation: nx0>nz0>ny0,
where nx0 denotes a refractive index at a slow axis of the
compensation film, ny0 denotes a refractive index at a fast axis of
the compensation film, and nz0 denotes a refractive index in a
direction perpendicular to the slow and fast axes of the compensation
film.

[0023] In an embodiment, the liquid crystal may be a reactive mesogen
liquid crystal.

[0024] In an embodiment, the reactive mesogen liquid crystal may include
at least one of a rod-shaped aromatic derivative having at least one
reactive cross-linking group, propylene glycol 1-methyl, propylene glycol
2-acetate, and a compound represented by P1-A1-(Z1-A2)n-P2, where P1 and
P2 independently include acrylate, methacrylate, vinyl, vinyloxy, epoxy
or a combination thereof, A1 and A2 include independently 1,4-phenylene,
naphthalene-2,6-diyl group, or a combination thereof, Z1 includes a
single bond, --COO--, --OCO-- or a combination thereof, and n is 0, 1 or
2.

[0025] According to another embodiment, an optical film including a
polarizer element and the compensation film is provided.

[0026] According to yet another embodiment, a display device includes a
display panel, a compensation film disposed on the display panel, and a
polarizer element disposed on the compensation film is provided, where
the compensation film includes a first retardation layer including a
polymer having negative birefringence, and a second retardation layer
including liquid crystal having positive birefringence, the first
retardation layer has an in-plane retardation (Re1) in a range of
about 320 nm to about 1050 nm for incident light having a wavelength of
about 550 nm, the second retardation layer has an in-plane retardation
(Re2) in a range of about 180 nm to about 910 nm for the incident
light having the wavelength of about 550 nm, an entire in-plane
retardation (Re0) of the first retardation layer and the second
retardation layer for the incident light having the wavelength of about
550 nm is a difference between the in-plane retardation (Re1) of the
first retardation layer and the in-plane retardation (Re2) of the
second retardation layer, the entire in-plane retardation (Re0) of
the first retardation layer and the second retardation layer for
wavelengths of about 450 nm, 550 nm, and 650 nm satisfies the following
inequation: Re0 (450 nm)<Re0 (550 nm)<Re0 (650 nm),
and an angle between a slow axis of the first retardation layer and a
slow axis of the second retardation layer is in a range of about 85
degrees to about 95 degrees.

[0027] In an embodiment, the first retardation layer may have a short
wavelength dispersion in a range of about 1.00 to about 1.15, the second
retardation layer may have a short wavelength dispersion in a range of
about 1.05 to about 1.30, the first retardation layer may have a long
wavelength dispersion in a range of about 0.90 to about 1.00, the second
retardation layer may have a long wavelength dispersion in a range of
about 0.80 to about 0.99, the entire short wavelength dispersion of the
first retardation layer and the second retardation layer may be greater
than or equal to about 0.7 and less than about 1.0, and the entire long
wavelength dispersion of the first retardation layer and the second
retardation layer may be greater than about 1.0 and less than or equal to
about 1.2.

[0028] In an embodiment, a thickness direction retardation (Rth1) and
the in-plane retardation (Re1) of the first retardation layer for
the incident light having the wavelength of about 550 nm may satisfy the
following Inequation: -2.0≦(Rth1/Re1)+0.5≦0.5, a
thickness direction retardation (Rth2) and the in-plane retardation
(Re2) of the second retardation layer for the incident light having
the wavelength of about 550 nm may satisfy the following Inequation:
1.0≧(Rth2/Re2)+0.5≧1.5, and the entire thickness
direction retardation (Rth0) and the entire in-plane retardation
(Re0) of the first retardation layer and the second retardation
layer for the incident light having the wavelength of about 550 nm may
satisfy the following inequation:
-1.0≦(Rth0/Re0)+0.5≦1.0.

[0029] In an embodiment, the first retardation layer may be an elongated
polymer layer including polystyrene, poly(styrene-co-maleic anhydride),
polymaleimide, poly(meth)acrylic acid, polyacrylonitrile,
polymethyl(meth)acrylate, cellulose ester,
poly(styrene-co-acrylonitrile), poly(styrene-co-maleimide),
poly(styrene-co-methacrylic acid), a derivative thereof, a copolymer
thereof, or a mixture thereof, and the second retardation layer may be an
anisotropic liquid crystal layer including a reactive mesogen liquid
crystal.

[0030] In an embodiment, the display panel may be a liquid crystal panel
or an organic light emitting panel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other features of the invention will become more
apparent by describing in detailed exemplary embodiments thereof with
reference to the accompanying drawings, in which:

[0032] FIG. 1 is a cross-sectional view schematically showing an
embodiment of a compensation film, according to the invention;

[0033] FIG. 2 is a top plan view schematically showing a slow axis of the
compensation film shown in FIG. 1;

[0034] FIG. 3 is a cross-sectional view schematically showing an
embodiment of an optical film, according to the invention;

[0035] FIG. 4 is a schematic view showing the anti-reflection principle of
showing an embodiment of an optical film, according to the invention;

[0036] FIG. 5 is a cross-sectional view schematically showing an
embodiment of an organic light emitting diode ("OLED") display, according
to the invention; and

[0037] FIG. 6 is a cross-sectional view schematically showing an
embodiment of a liquid crystal display ("LCD") device, according to the
invention;

DETAILED DESCRIPTION

[0038] The invention now will be described more fully hereinafter with
reference to the accompanying drawings, in which various embodiments are
shown. This invention may, however, be embodied in many different forms,
and should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this disclosure
will be thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like reference numerals refer to
like elements throughout.

[0039] It will be understood that when an element is referred to as being
"on" another element, it can be directly on the other element or
intervening elements may be therebetween. In contrast, when an element is
referred to as being "directly on" another element, there are no
intervening elements present.

[0040] It will be understood that, although the terms "first," "second,"
"third" etc. may be used herein to describe various elements, components,
regions, layers and/or sections, these elements, components, regions,
layers and/or sections should not be limited by these terms. These terms
are only used to distinguish one element, component, region, layer or
section from another element, component, region, layer or section. Thus,
"a first element," "component," "region," "layer" or "section" discussed
below could be termed a second element, component, region, layer or
section without departing from the teachings herein.

[0041] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As used
herein, the singular forms "a," "an," and "the" are intended to include
the plural forms, including "at least one," unless the content clearly
indicates otherwise. "Or" means "and/or." As used herein, the term
"and/or" includes any and all combinations of one or more of the
associated listed items. It will be further understood that the terms
"comprises" and/or "comprising," or "includes" and/or "including" when
used in this specification, specify the presence of stated features,
regions, integers, steps, operations, elements, and/or components, but do
not preclude the presence or addition of one or more other features,
regions, integers, steps, operations, elements, components, and/or groups
thereof.

[0042] Furthermore, relative terms, such as "lower" or "bottom" and
"upper" or "top," may be used herein to describe one element's
relationship to another element as illustrated in the Figures. It will be
understood that relative terms are intended to encompass different
orientations of the device in addition to the orientation depicted in the
Figures. For example, if the device in one of the figures is turned over,
elements described as being on the "lower" side of other elements would
then be oriented on "upper" sides of the other elements. The exemplary
term "lower," can therefore, encompasses both an orientation of "lower"
and "upper," depending on the particular orientation of the figure.
Similarly, if the device in one of the figures is turned over, elements
described as "below" or "beneath" other elements would then be oriented
"above" the other elements. The exemplary terms "below" or "beneath" can,
therefore, encompass both an orientation of above and below.

[0043] "About" or "approximately" as used herein is inclusive of the
stated value and means within an acceptable range of deviation for the
particular value as determined by one of ordinary skill in the art,
considering the measurement in question and the error associated with
measurement of the particular quantity (i.e., the limitations of the
measurement system). For example, "about" can mean within one or more
standard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

[0044] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this disclosure
belongs. It will be further understood that terms, such as those defined
in commonly used dictionaries, should be interpreted as having a meaning
that is consistent with their meaning in the context of the relevant art
and the disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.

[0045] Exemplary embodiments are described herein with reference to cross
section illustrations that are schematic illustrations of idealized
embodiments. As such, variations from the shapes of the illustrations as
a result, for example, of manufacturing techniques and/or tolerances, are
to be expected. Thus, embodiments described herein should not be
construed as limited to the particular shapes of regions as illustrated
herein but are to include deviations in shapes that result, for example,
from manufacturing. For example, a region illustrated or described as
flat may, typically, have rough and/or nonlinear features. Moreover,
sharp angles that are illustrated may be rounded. Thus, the regions
illustrated in the figures are schematic in nature and their shapes are
not intended to illustrate the precise shape of a region and are not
intended to limit the scope of the claims.

[0046] Hereinafter, an embodiment of a compensation film according to the
invention will be described referring to FIG. 1.

[0047] FIG. 1 is a cross-sectional view schematically showing an
embodiment of a compensation film, according to the invention.

[0048] Referring to FIG. 1, an embodiment of the compensation film 100
includes a first retardation layer 110 and a second retardation layer
120.

[0049] The first retardation layer 110 is an elongated polymer layer
including a polymer having negative birefringence, and the second
retardation layer 120 is an anisotropic liquid crystal layer including a
liquid crystal having positive birefringence. The birefringence
(Δn) is a difference found by subtracting the refractive index
(no) of light propagating perpendicular to an optical axis from the
refractive index (ne) of light propagating parallel to the optical
axis, and the first retardation layer 110 and the second retardation
layer 120 have opposite-sign birefringences from each other, e.g.,
positive birefringence and negative birefringence, respectively, or vice
versa.

[0050] The polymer having a negative birefringence may include, for
example, polystyrene, poly(styrene-co-maleic anhydride), polymaleimide,
poly(meth)acrylic acid, polyacrylonitrile, polymethyl(meth)acrylate,
cellulose ester, poly(styrene-co-acrylonitrile),
poly(styrene-co-maleimide), poly(styrene-co-methacrylic acid), or a
combination thereof (e.g., a derivative thereof, a copolymer thereof, or
a mixture thereof), but is not limited thereto.

[0051] The first retardation layer 110 may maintain the negative
birefringence after being elongated.

[0052] The liquid crystal may be a monomer, an oligomer, or a polymer
having a rigid-rod shape. The liquid crystal may be aligned in a
predetermined direction along the optical axis.

[0053] The liquid crystal may be a reactive mesogen liquid crystal and may
have, for example, a reactive cross-linking group. The reactive mesogen
liquid crystal may include, for example, a rod-shaped aromatic derivative
having at least one reactive cross-linking group, propylene glycol
1-methyl, propylene glycol 2-acetate, and a compound represented by
P1-A1-(Z1-A2)n-P2, or a combination thereof, but is not limited thereto.
Here, P1 and P2 independently include acrylate, methacrylate, vinyl,
vinyloxy, epoxy or a combination thereof, A1 and A2 independently include
1,4-phenylene, naphthalene-2,6-diyl group or a combination thereof, Z1
includes a single bond, --COO--, --OCO-- or a combination thereof, and n
is 0, 1 or 2.

[0054] In such an embodiment, the compensation properties may be
strengthened by adjusting the optical properties of the first retardation
layer 110 and the second retardation layer 120 to reduce the wavelength
dependency and the viewing angle dependency of the compensation film 100
including the first retardation layer 110 and the second retardation
layer 120.

[0055] In an embodiment, the first retardation layer 110 and second
retardation layer 120 may have a forward wavelength dispersion
retardation, and the compensation film 100 including the first
retardation layer 110 and the second retardation layer 120 may have a
reverse wavelength dispersion retardation. The forward wavelength
dispersion retardation has higher retardation to light having a short
wavelength than retardation to light having a long wavelength, and the
reverse wavelength dispersion retardation has higher retardation to light
having a long wavelength than retardation to light having a short
wavelength.

[0056] The retardation may be referred to as in-plane retardation
(Re), and the in-plane retardation (Re) may be represented by
Re=(nx-ny)d. Herein, nx denotes a refractive index in
a direction having a highest refractive index in a plane of a film
(hereinafter referred to as "slow axis"), ny denotes a refractive
index in a direction having a lowest refractive index in a plane of a
film (hereinafter referred to as "fast axis"), and d denotes a thickness
of film.

[0057] The in-plane retardation (Re1) of the first retardation layer
110 may be represented by Re1=(nx1-ny1)d1, the
in-plane retardation (Re2) of the second retardation layer 120 may
be represented by Re2=(nx2-ny2)d2, and the in-plane
retardation (Re0) of the compensation film 100 may be represented by
Re0=(nx0-ny0)d0. Herein, nx1 denotes a
refractive index at the slow axis of the first retardation layer 110,
ny1 denotes a refractive index at the fast axis of the first
retardation layer 110, d1 denotes a film thickness of the first
retardation layer 110, nx2 denotes a refractive index at the slow
axis of the second retardation layer 120, ny2 denotes a refractive
index at the fast axis of the second retardation layer 120, d2
denotes a film thickness of the second retardation layer 120, nx0
denotes a refractive index at the slow axis of the compensation film 100,
ny0 denotes a refractive index at the fast axis of the compensation
film 100, and d0 denotes a film thickness of the compensation film
100. Accordingly, the in-plane retardation (Re1, Re2) may be
provided within a predetermined range by changing a thickness and/or a
refractive index at the slow axis and/or the fast axis of the first
retardation layer 110 and the second retardation layer 120.

[0058] According to an embodiment, the first retardation layer 110 may
have an in-plane retardation (Re1) in a range of about 320
nanometers (nm) to about 1050 nm for incident light having a wavelength
of about 550 nm (hereinafter referred to as a "reference wavelength"),
the second retardation layer 120 may have an in-plane retardation
(Re2) in a range of about 180 nm to about 910 nm for the incident
light having the reference wavelength, and the entire in-plane
retardation of the first retardation layer 110 and the second retardation
layer 120, which is the in-plane retardation (Re0) of the
compensation film 100, for the incident light having the reference
wavelength may be equal to the difference between the in-plane
retardation (Re1) of the first retardation layer 110 and the
in-plane retardation (Re2) of the second retardation layer 120. In
one embodiment, for example, the compensation film 100 may have an
in-plane retardation (Re0) in a range of about 120 nm to about 160
nm for the incident light having the reference wavelength.

[0059] In the first retardation layer 110 and the second retardation layer
120, the retardation of light having a short wavelength may be higher
than the retardation of light having a long wavelength, as described
above. In one embodiment, for example, the in-plane retardation
(Re1) of the first retardation layer 110 for the wavelengths of 450
nm, 550 nm, and 650 nm may satisfy the following inequation: Re1
(450 nm)≧Re1 (550 nm)>Re1 (650 nm) or Re1 (450
nm)>Re1 (550 nm)≧Re1 (650 nm), and the in-plane
retardation (Re2) of the second retardation layer 120 may satisfy
the following inequation: Re2 (450 nm)>Re2 (550
nm)>Re2 (650 nm).

[0060] The changing of the retardation of the short wavelength for the
reference wavelength may be referred to as short wavelength dispersion,
the short wavelength dispersion of the first retardation layer 110 may be
represented by Re1 (450 nm)/Re1 (550 nm), and the short
wavelength dispersion of the second retardation layer 120 may be
represented by Re2 (450 nm)/Re2 (550 nm). In one embodiment,
for example, the first retardation layer 110 may have a short wavelength
dispersion in a range of about 1.00 to about 1.15, and the second
retardation layer 120 may have a short wavelength dispersion in a range
of about 1.05 to about 1.30.

[0061] The changing of the retardation of the long wavelength for the
reference wavelength may be referred to as long wavelength dispersion,
the long wavelength dispersion of the first retardation layer 110 may be
represented by Re1 (650 nm)/Re1 (550 nm), and the long
wavelength dispersion of the second retardation layer 120 may be
represented by Re2 (650 nm)/Re2 (550 nm). In one embodiment,
for example, the first retardation layer 110 may have a long wavelength
dispersion in a range of about 0.90 to about 1.00, and the second
retardation layer 120 may have a long wavelength dispersion in a range of
about 0.80 to about 0.99.

[0062] In an embodiment, an angle between the slow axis of the first
retardation layer 110 and the slow axis of the second retardation layer
120 may be in a range of about 85 degrees to about 95 degrees.

[0063] FIG. 2 is a top plan view schematically showing a slow axis of the
compensation film shown in FIG. 1.

[0064] Referring to FIG. 2, the angle between the slow axis 115 of the
first retardation layer 110 and the slow axis 125 of the second
retardation layer 120 may be in a range of about 85 degrees to about 95
degrees, for example, about 87.5 degrees to about 92.5 degrees, or may be
about 90 degrees.

[0065] When the first retardation layer 110 and the second retardation
layer 120 have the in-plane retardation, and when the angle between the
slow axis 115 of the first retardation layer 110 and the slow axis 125 of
the second retardation layer 120 is in the range of about 85 degrees to
about 95 degrees, the compensation film 100 may have a reverse wavelength
dispersion retardation.

[0066] As described above, in an embodiment, the in-plane retardation
(Re0) of the compensation film 100 for the incident light having the
reference wavelength may be the difference between the in-plane
retardation (Re1) of the first retardation layer 110 and the
in-plane retardation (Re2) of the second retardation layer 120, and
the in-plane retardation (Re0) of the compensation film 100 for the
incident light having the reference wavelength may be in a range of, for
example, about 120 nm to about 160 nm.

[0067] The in-plane retardation (Re0) of the compensation film 100
for the wavelengths of 450 nm, 550 nm, and 650 nm may satisfy the
following inequation: Re0 (450 nm)<Re0 (550 nm)<Re0
(650 nm), to provide a reverse wavelength dispersion retardation.

[0068] The short wavelength dispersion of the compensation film 100 may be
represented by Re0 (450 nm)/Re0 (550 nm), for example, greater
than or equal to about 0.7 and less than about 1.0. The compensation film
100 may have a short wavelength dispersion in the range of, for example,
about 0.75 to about 0.90, or may have a short wavelength dispersion of
about 0.81.

[0069] The long wavelength dispersion of the compensation film 100 may be
represented by Re0 (650 nm)/Re0 (550 nm), for example, greater
than about 1.0 and less than or equal to about 1.2. The compensation film
100 may have a long wavelength dispersion in a range of, for example,
about 1.15 to about 1.19, or a long wavelength dispersion of about 1.18.

[0070] In such an embodiment, the retardation includes thickness direction
retardation (Rth) besides the in-plane retardation (Re). The
thickness direction retardation (Rth) is retardation generated in a
thickness direction of a film, and the thickness direction retardation
(Rth1) of the first retardation layer 110 may be represented by
Rth1=[{(nx1+ny1)/2}-nz1]d1, the thickness
direction retardation (Rth2) of the second retardation layer 120 may
be represented by Rth2=[{(nx2+ny2)/2}-nz2]d2,
and the thickness direction retardation (Rth0) of the compensation
film 110 may be represented by
Rth0=[{(nx0+ny0)/2}-nz0]d0. Herein nx1
denotes a refractive index at a slow axis of the first retardation layer
110, ny1 denotes a refractive index at a fast axis of the first
retardation layer 110, nz1 denotes a refractive index in the
direction perpendicular to the slow and fast axes of the first
retardation layer 110, nx2 denotes a refractive index at a slow axis
of the second retardation layer 120, ny2 denotes a refractive index
at a fast axis of the second retardation layer 120, and nz2 denotes
a refractive index in the direction perpendicular to the slow and fast
axes of the second retardation layer 120, and nx0 denotes a
refractive index at a slow axis of the compensation film 100, ny0
denotes a refractive index at a fast axis of the compensation film 100,
and nz0 denotes a refractive index in a direction perpendicular to
the slow and fast axes of the compensation film 100.

[0071] The thickness direction retardation (Rth0) of the compensation
film 100 may be represented by the sum of the thickness direction
retardation (Rth1) of the first retardation layer 110 and the
thickness direction retardation (Rth2) of the second retardation
layer 120. As the thickness direction retardation (Rth0) of the
compensation film 100 is decreased, the viewing angle dependency may be
reduced.

[0072] The thickness direction retardation (Rth1) and the in-plane
retardation (Re1) of the first retardation layer 110 for the
incident light having the reference wavelength satisfy the following
Inequation 1, and the thickness direction retardation (Rth2) and the
in-plane retardation (Re2) of the second retardation layer 120 for
the incident light having the reference wavelength satisfy the following
Inequation 2.

-2.0≦(Rth1/Re1)+0.5≦0.5 Inequation 1:

1.0≦(Rth2/Re2)+0.5≦1.5 Inequation 2:

[0073] When the first retardation layer 110 and the second retardation
layer 120 satisfy Inequations 1 and 2, the compensation film 100 may
satisfy the following Inequation 3 by offsetting the thickness direction
retardation (Rth1) of the first retardation layer 110 and the
thickness direction retardation (Rth2) of the second retardation
layer 120.

-1.0≦(Rth0/Re0)+0.5≦1.0 Inequation 3:

[0074] In addition, the first retardation layer 110 has a refractive index
simultaneously satisfying the following Inequations 4 and 5, and the
second retardation layer 120 has a refractive index simultaneously
satisfying the following Inequations 6 and 7.

nx1≧ny1 Inequation 4:

nx1≧nz1 Inequation 5:

[0075] In Inequations 4 and 5, nx1 denotes a refractive index at a
slow axis of the first retardation layer, ny1 denotes a refractive
index at a fast axis of the first retardation layer, and nz1 denotes
a refractive index in the direction perpendicular to the slow and fast
axes of the first retardation layer.

nx2≧ny2 Inequation 6:

nx2≧nz2 Inequation 7:

[0076] In Inequations 6 and 7, nx2 denotes a refractive index at a
slow axis of the second retardation layer, ny2 denotes a refractive
index at a fast axis of the second retardation layer, and nz2
denotes a refractive index in the direction perpendicular to the slow and
fast axes of the second retardation layer.

[0077] In an embodiment, where the first retardation layer 110 and the
second retardation layer 120 have the refractive index satisfying the
equations above, the compensation film 110 may have a refractive index
satisfying the following Inequation 8.

nx0>nz0>ny0 Inequation 8:

[0078] In the Inequation 8, nx0 denotes a refractive index at a slow
axis of the compensation film, ny0 denotes a refractive index at a
fast axis of the compensation film, and nz0 denotes a refractive
index in a direction perpendicular to the slow and fast axes of the
compensation film.

[0079] The compensation film 100 may effectively offset the thickness
direction retardation (Rth0) and simultaneously provide λ/4
retardation in the entire visible ray region by assembling the first
retardation layer 110 and the second retardation layer 120 and by
controlling the optical properties to accomplish the reverse wavelength
dispersion retardation. Accordingly, an embodiment of the compensation
film 100 may effectively accomplish the circularly polymerized
compensation function and may improve the display characteristics of the
display device including the compensation film 100.

[0080] The compensation film 100 may further include an adhesion layer
(not shown) between the first retardation layer 110 and the second
retardation layer 120. The adhesion layer may effectively attach the
first retardation layer 110 and the second retardation layer 120, and may
include or be made of, for example, a pressure sensitive adhesive.

[0081] The compensation film 100 may be manufactured by preparing each of
the first retardation layer 110 and the second retardation layer 120 as a
film and assembling the first and second retardation layers 110 and 120,
or by coating the second retardation layer 120 on the first retardation
layer 110. When preparing the second retardation layer 120 as a film, a
liquid crystal solution may be coated on a support layer and irradiated
to be cross-linked. The support layer may be, for example, a triacetyl
cellulose ("TAC") film, but is not limited thereto. The compensation film
100 may be provided or formed by, for example, roll-to-roll coating, spin
coating, transferring, and the like, but is not limited thereto.

[0082] The compensation film 100 may be provided into an optical film
together with a polarizer. The optical film may be, for example, an
anti-reflective film.

[0083] FIG. 3 is a cross-sectional view schematically showing an
embodiment of an optical film, according to the invention.

[0084] Referring to FIG. 3, an embodiment of the optical film 300 includes
a compensation film 100 and a polarizer 200 disposed on a side (e.g., an
upper surface) of the compensation film 100.

[0085] The compensation film 100 of the optical film 300 is substantially
the same as an embodiment thereof as described above, and the first
retardation layer 110 may be disposed to contact the polarizer 200, or
the second retardation layer 120 may be disposed to contact the polarizer
200.

[0086] The polarizer 200 may be disposed on the side where the light
enters, and may be a linear polarizer for shifting the polarization of
incident light into linear polarization. The polarizer 200 may include or
be made of, for example, elongated polyvinyl alcohol ("PVA") and the
polarizer 200 may be prepared by a method including, for example, drawing
a PVA film, adsorbing iodine or a dichroic dye thereto, and borating and
washing the PVA film.

[0087] The optical film 300 may further include a protective layer (not
shown) on a surface of the polarizer 200. The protective layer may be
provided for further reinforcing the functionality or improving the
durability of the optical film 300, or for reducing reflection or glare,
and for example, may be a TAC film, but is not limited thereto.

[0088] The optical film 300 may further include a correction layer (not
shown) disposed on the compensation film 100. The correction layer may
be, for example, a color shift resistant layer, but is not limited
thereto.

[0089] The optical film 300 may further include a light blocking layer
(not shown) which extends along the edge. The light blocking layer may
have a strip shape and may be disposed along the circumference of the
optical film 300. In one embodiment, for example, the light blocking
layer may be disposed between the first retardation layer 110 and the
second retardation layer 120 of the compensation film 100. The light
blocking layer may include an opaque material, for example, a black
material. In one embodiment, for example, the light blocking layer may
include or be made of a black ink.

[0090] The optical film 300 may be stacked with a compensation film 100
and a polarizer 200 according to a roll-to-roll method, but is not
limited thereto.

[0091] FIG. 4 is a schematic view showing the anti-refractive principle of
an embodiment of an optical film, according to the invention.

[0092] Referring to FIG. 4, while the incident unpolarized light having
entered from the outside is passing through a polarizer 200, the
unpolarized light is polarized. Then, the polarized light is shifted into
circularly polarized light by passing through the compensation film 100,
only a first polarized perpendicular component, which is a polarized
perpendicular component of two polarized perpendicular components, is
transmitted. While the circularly polarized light is reflected in a
display panel 40 including a substrate, an electrode, and so on, the
circular polarization direction of the circularly polarized light is
changed, and the circularly polarized light is passed through the
compensation film 100 again, such that only a second polarized
perpendicular component, which is the other polarized perpendicular
component of the two polarized perpendicular components, may be
transmitted. As the second polarized perpendicular component is blocked
by the polarizer 200, light does not exit to the outside, thereby
effectively preventing the external light reflection.

[0093] The compensation film 100 and the optical film 200 may be applied
to various display devices.

[0094] An embodiment of the display device includes a display panel, a
compensation film disposed on a side (or a surface) of the display panel,
and a polarizer element disposed on a side (or a surface) of the
compensation film. The display panel may be a liquid crystal display
panel or an organic light emitting display panel, but is not limited
thereto.

[0095] Hereinafter, an embodiment of a display panel, where the display
panel is an organic light emitting diode ("OLED") display will be
described with reference to FIG. 5.

[0096] FIG. 5 is a cross-sectional view showing an embodiment of an OLED
display according to the invention.

[0097] Referring to FIG. 5, an embodiment of the OLED display includes an
organic light emitting panel 400, a compensation film 100 disposed on a
side (e.g., an upper side) of OLED panel 400, and a polarization device
200 disposed on a side (e.g., an upper side) of the compensation film
100.

[0098] The OLED panel 400 may include a base substrate 410, a lower
electrode 420, an organic emission layer 430, an upper electrode 440 and
an encapsulation substrate 450.

[0099] The base substrate 410 may include or be made of glass or plastic,
for example.

[0100] One of the lower electrode 420 and the upper electrode 440 may be
an anode, and the other of the lower electrode 420 and the upper
electrode 440 may be a cathode. The anode is an electrode injected with
holes, and may include or be made of a transparent conductive material
having a high work function to transmit the emitted light to the outside,
for example, indium tin oxide ("ITO") or indium zinc oxide ("IZO"). The
cathode is an electrode injected with electrons, and may be made of a
conductive material having a low work function and not affecting the
organic material, and may include, for example, aluminum (Al), calcium
(Ca), barium (Ba) or a combination thereof.

[0101] The organic emission layer 430 includes an organic material which
may emit light when applying a voltage to the lower electrode 420 and the
upper electrode 440.

[0102] An auxiliary layer (not shown) may be further provided between the
lower electrode 420 and the organic emission layer 430 and between the
upper electrode 440 and the organic emission layer 430. The auxiliary
layer is used to balance electrons and holes, and may include a hole
transport layer ("HTL"), a hole injection layer ("HIL"), an electron
injection layer ("EIL"), and an electron transporting layer ("ETL").

[0103] The encapsulation substrate 450 may include or be made of glass,
metal, or a polymer, and may seal the lower electrode 420, the organic
emission layer 430, and the upper electrode 440 to effectively prevent
moisture and/or oxygen inflow from the outside.

[0104] The compensation film 100 and the polarizer 200 may be disposed on
the side emitting light. In one embodiment, for example, where the OLED
display has bottom emission structure, in which light is emitted at the
side of the base substrate 410, the compensation film 100 and the
polarizer 200 may be disposed on the exterior side of the base substrate
410. In one alternative embodiment, for example, where the OLED display
has a top emission structure, in which light is emitted at the side of
the encapsulation substrate 450, the compensation film 100 and the
polarizer 200 may be disposed on the exterior side of the encapsulation
substrate 450.

[0105] The compensation film 100 and the polarizer 200 shown in FIG. 5 are
substantially the same as the compensation film 100 and the polarizer 200
of the embodiments shown in FIG. 3 described above, and may function as
an anti-reflective film for effectively preventing light passing through
the polarizer 200 from being reflected by a metal such as an electrode of
the organic light emitting panel 400 and emitted outside of the display
device. In such an embodiment, the compensation film 100 may reduce the
viewing angle dependency as described above to improve the side viewing
angle as well as the front viewing angle. Accordingly, the display
characteristics of the OLED display may be improved.

[0106] Hereinafter, an embodiment of a display panel, where the display
panel is a liquid crystal display ("LCD") will be described with
reference to FIG. 6.

[0107] FIG. 6 is a cross-sectional view schematically showing an
embodiment of an LCD, according to the invention.

[0108] Referring to FIG. 6, an embodiment of the LCD includes a liquid
crystal display panel 500, a compensation film 100 disposed on a side
(e.g., an upper side or a lower side) of the liquid crystal panel 500,
and a polarizer element 200 disposed on a side (e.g., an upper side or a
lower side) of the compensation film 100.

[0110] The liquid crystal panel 500 may include a first display panel 510,
a second display panel 520, and a liquid crystal layer 530 interposed
between the first display panel 510 and the second display panel 520.

[0111] The first display panel 510 may include, for example, a thin film
transistor (not shown) disposed on a substrate (not shown) and a first
electric field generating electrode (not shown) connected to the thin
film transistor, and the second display panel 520 may include, for
example, a color filter (not shown) disposed on a substrate (not shown)
and a second electric field generating electrode (not shown), but it is
not limited thereto. In an alternative embodiment, the color filter may
be included in the first display panel 510, while the first electric
field generating electrode and the second electric field generating
electrode may be disposed on the first display panel 510 together
therewith.

[0112] In an embodiment, the liquid crystal layer 530 may include a
plurality of liquid crystal molecules. The liquid crystal molecules may
have positive or negative dielectric anisotropy. In an embodiment, where
the liquid crystal molecules have positive dielectric anisotropy, the
major axes thereof may be aligned substantially parallel to the surface
of the first display panel 510 and the second display panel 520 when an
electric field is not applied thereto, and the major axes may be aligned
substantially perpendicular to the surface of the first display panel 510
and second display panel 520 when an electric field is applied thereto.
In an alternative embodiment, where the liquid crystal molecules have
negative dielectric anisotropy, the major axes may be aligned
substantially perpendicular to the surface of the first display panel 510
and the second display panel 520 when an electric field is not applied
thereto, and the major axes may be aligned substantially parallel to the
surface of the first display panel 510 and the second display panel 520
when an electric field is applied thereto.

[0113] The compensation film 100 and the polarizer 200 are disposed on the
outside of the liquid crystal panel 500. In an embodiment, as shown in
FIG. 6, the compensation film 100 and the polarizer 200 may be disposed
on both the lower part and the upper part of the liquid crystal panel
500, but they are not limited thereto. In an alternative embodiment, the
compensation film 100 and the polarizer 200 may be disposed on only one
of the lower part and the upper part of liquid crystal panel 500.

[0114] Hereinafter, the disclosure will be illustrated in more detail with
reference to examples. However, these examples are exemplary, and the
disclosure is not limited thereto.

Manufacture of Compensation Film

PREPARATION EXAMPLE 1

[0115] (1) Preparation of First Retardation Layer (A)

[0116] A poly(styrene-co-methacrylic acid) film (T080, manufactured by
TOYO STYRENE) having a thickness of 100 μm is elongated in one axial
direction (using a tension tester manufactured by Instron) at about
128° C. at a ratio of 50%to 200% to provide a first retardation
layer (A) having optical properties shown in the following Table 1.

[0117] (2) Preparation of Second Retardation Layer (B)

[0118] A 60 μm-thick Z-TAC film (from Fuji Film) is rubbed in one
direction and coated with +A plate liquid crystal (RMS03-013C, Merck &
Co., Inc.) in a thickness of about 5 μm to about 10 μm and dried in
a drying oven at 60° C. for one minute to remove a coating
solvent. Subsequently, ultraviolet ("UV") rays are irradiated thereto at
80 milliwatts per square centimeter (mW/cm2) for 30 seconds in a
nitrogen-charged container, so that the liquid crystal molecules are is
photo-cross-linked to provide a second retardation layer (B) having the
optical properties shown in the following Table 1.

[0120] Subsequently, the first retardation layer is disposed to face the
liquid crystal layer of the second retardation layer. The first and
second retardation layers are disposed to provide an angle between the
slow axis of the first retardation layer and the slow axis of the second
retardation layer to be about 90 degrees. Subsequently, a liquid crystal
layer is transcribed on one side of the first retardation layer, and a
Z-TAC film is removed to provide a compensation film (AB) assembled with
the first retardation layer and the second retardation layer.

[0121] A compensation film is manufactured in accordance with the same
procedure as in Preparation Example 1, except that the first retardation
layer (A) and the second retardation layer (B) have the optical
properties shown in the following Table 2.

[0122] A compensation film is manufactured in accordance with the same
procedure as in Preparation Example 1, except that the first retardation
layer (A) and the second retardation layer (B) have the optical
properties shown in the following Table 3.

[0123] A compensation film is manufactured in accordance with the same
procedure as in Preparation Example 1, except that the first retardation
layer (A) and the second retardation layer (B) have the optical
properties shown in the following Table 4.

[0124] A compensation film is manufactured in accordance with the same
procedure as in Preparation Example 1, except that the first retardation
layer (A) and the second retardation layer (B) have the optical
properties shown in the following Table 5.

[0126] A cycloolefin polymer (manufactured by ZEON) film having a
thickness of 100 μm is elongated in one axial direction (using a
tension tester manufactured by Instron) at about 140° C. at a
ratio of 70% to provide a first retardation layer (A-1) having optical
properties shown in the following Table 6.

[0127] (2) Preparation of Second retardation layer (B-1)

[0128] A Z-TAC film (Fuji Film) having a thickness of 60 μm is rubbed
in one direction and coated with +A plate liquid crystal (RMS03-013C,
Merck & Co., Inc.) in a thickness of about 10 μm and dried in a drying
oven at 60° C. for one minute to remove a coating solvent.
Subsequently, UV rays are irradiated thereto at 80 mW/cm2 for 30
seconds in a nitrogen-charged container to provide a second retardation
layer (B-1) having the optical properties shown in the following Table 6.

[0130] Subsequently, the first retardation layer is disposed to face the
liquid crystal layer of the second retardation layer. The first and
second retardation layers are arranged to provide an angle between the
slow axis of the first retardation layer and the slow axis of the second
retardation layer to be about 90 degrees. Subsequently, a liquid crystal
layer is transcribed on one side of the first retardation layer, and a
Z-TAC film is removed to provide a compensation film (A-1/B-1) assembled
with the first retardation layer and the second retardation layer.

[0131] The compensation films (AB) according to Preparation Examples 1 to
5 are evaluated for in-plane retardation, thickness direction retardation
and wavelength dispersion. The in-plane retardation, the thickness
direction retardation and the wavelength dispersion are measured using
AxoScan equipment (manufactured by Axometrics). The measured wavelength
ranges from about 400 nm to about 700 nm, and the film retardation is
measured by adjusting the incident angle in a range from about -70
degrees to about 70 degrees at an interval of 5 degrees.

[0133] Referring to Table 7, an exemplary embodiment of the compensation
films, e.g., Preparation Examples 1 to 5, may have the reverse wavelength
dispersion retardation, and the viewing angle dependency may be improved
by satisfying the range of -1.0≦Nz≦1.0 and sufficiently
offsetting the thickness direction retardation.

Manufacture of OLED Display

EXAMPLE 1

[0134] An organic light emitting display panel having a structure
sequentially stacked on a glass substrate with a cathode including a
metallic electrode material, an organic emission layer including a light
emitting material, an anode including a transparent conductivity
material, and an upper substrate. The compensation film according to
Preparation Example 1 and a polarizer (manufactured by Cheil Industries
Inc.) are sequentially attached to the upper substrate of the organic
light emitting display panel to provide an OLED display.

COMPARATIVE EXAMPLE 1

[0135] An OLED display is manufactured in accordance with the same
procedure as in Example 1, except using the compensation film according
to Comparative Preparation Example 1 instead of the compensation film
according to Preparation Example 1.

Evaluation 2

[0136] The OLED displays according to Example 1 and Comparative Example 1
are evaluated for a reflectance and a color shift at the front. The color
shift uses a horizontal axis of a* value and a vertical axis of b* value,
where a positive a* value means red, a negative a* value means green, a
positive b* value means yellow, a negative b* value means blue, and as
absolute values of a* and b* are higher, the color is darker. The smaller
a*, b* and Δa* b* values are, the better the color shift is.

[0137] The reflectance and the color shift at the front side are evaluated
by supplying light under the conditions of a D65 light source, reflection
of 8 degrees, and a light receiving part of 2 degrees, and using a
spectrum colorimeter (CM-3600d, manufactured by Konica Minolta).

[0139] Referring to Table 8, the OLED display according to Example 1 has
similar front reflectance and significantly improved color shift compared
to the OLED display according to Comparative Example 1. Specifically, the
OLED display according to Example 1 has similar front reflectance and
improved the color shift by 1.80 compared to the OLED display according
to Comparative Example 1.

Evaluation 3

[0140] The OLED displays according to Example 1 and Comparative Example 1
are evaluated for reflectance and color shift at the side. The
reflectance and the color shift at the side are evaluated by EZContrast
equipment (manufactured by ELDIM).

[0142] Referring to Table 9, the OLED display according to Example 1
significantly improves the side reflectance and color shift compared to
the OLED display according to Comparative Example 1. Accordingly, an
exemplary embodiment of the OLED display, e.g., the OLED display
according to Example 1, may significantly reduce the viewing angle
dependency.

[0143] While this disclosure has been described in connection with what is
presently considered to be practical exemplary embodiments, it is to be
understood that the invention is not limited to the disclosed
embodiments, but, on the contrary, is intended to cover various
modifications and equivalent arrangements included within the spirit and
scope of the appended claims.

Patent applications by Hyung Jun Kim, Suwon-Si KR

Patent applications by Myung-Sup Jung, Seongnam-Si KR

Patent applications by Sang Ah Gam, Seoul KR

Patent applications by SAMSUNG ELECTRONICS CO., LTD.

Patent applications in class For compensation of birefringence effects

Patent applications in all subclasses For compensation of birefringence effects